Background
The long non-coding (lncRNA) RNA MALAT1 (metastasis-associated lung adenocarcinoma transcript 1) is known to promote tumorigenesis, whereas microRNA-145 (miR-145) plays an antitumor role in several cancers. In this study, we aimed to elucidate the role of MALAT1 and miR-145 in prostate cancer cells and investigate the effect of MALAT1 downregulation on prostate cancer (PCa) cells in vitro in vivo.
Conclusions
We confirmed that MALAT1 acts as a competing endogenous RNA (ceRNA) of miR-145. The MALAT1 based regulation of MiR-145-5p-SMAD3/TGFBR2 interactions could be an intriguing molecular pathway for the progression of PCa.
Methods
The Cancer Genome Atlas (TCGA) datasets were used to carry out the initial bioinformatics analysis; the findings were then tested in LNCaP and CWR22Rv1 cell lines. Western blot and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to evaluate the levels of MALAT1 and miR-145 along with related biomarkers. Furthermore, wound-healing and Transwell assays were performed to test the migratory and invasive abilities of PCa cells. Luciferase reporter assays were used to validate the relationship between MALAT1 and miR-145; their down-stream target genes were also studied. To further substantiate these findings in an animal model, tumor studies including immunofluorescence staining of tissues were carried in nude mice.
Results
The expression of MALAT1 was upregulated in both LNCaP cell lines and CWR22Rv1 cell lines (F=2.882, t=13.370, P<0.001; F=2.268, t=15.859, P<0.001). Knockdown of MALAT1 reduced the migratory and invasive capabilities of PCa cells (F=0.017, t=12.212, P<0.001; F=10.723, t=6.016, P=0.002). Using direct binding, MALAT1 suppressed the antitumor function of miR-145, which in turn upregulated transforming growth factor-β1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) via SMAD3 and TGFBR2 (F=2.097, t=5.389, P=0.006; F=1.306, t=4.155, P=0.014). Conclusions: We confirmed that MALAT1 acts as a competing endogenous RNA (ceRNA) of miR-145. The MALAT1 based regulation of MiR-145-5p-SMAD3/TGFBR2 interactions could be an intriguing molecular pathway for the progression of PCa.